Chad Johnson Contacts F.B.I Over Leaked Sex Tape

Chad Johnson is turning to the FBI for help … after a sex tape featuring the former NFL star leaked onto the Internet, TMZ has learned.

The footage shows Chad in a Florida hotel room … doing the dirty with a tatted-up female.

Chad believes the video was hacked from his phone — much like Scarlett Johansson’s nude photos. So, like Scarlett, he’s contacted the FBI to help hunt down the culprit.

TMZ broke the story … Chad admits the tape is real but insists he’s not the one who leaked it. He says it was shot more than 3 years ago.

We’re told Chad’s still waiting for a response from the Bureau — but he’s not sitting around … he’s contacted his lawyer to put together a cease-and-desist letter to get the footage yanked from the web.